Evaluation of genetic resources of hard red spring wheat with highly dormant seeds and their application in breeding

Pre-harvest sprouting and high alpha-amylase activity of seeds are the most serious problems of wheat production in Hokkaido. There has been an increase in the frequency with which several days of continuous rain have occurred at the time of wheat harvest. In addition, low temperatures, i.e., below 15degC, combined with rainfall, accelerate the damage due to pre-harvest sprouting of wheat. Pre-harvest sprouting cannot be easily controlled using chemical or agricultural methods. The most effective means of controlling this damage is by breeding resistant cultivars. Resistance of hard red spring wheat to pre-harvest sprouting was evaluated among the following lines: OS38-5, OS68, OS70 and OS71 derived from OS21-5. The spring wheat OS21-5 has highly dormant seeds that are continuously selected through early generation for low-temperature ungerminability. The seeds of the OS-lines are highly dormant and highly resistant to pre-harvest sprouting at 15degC; further, a high falling number was maintained for 7 days during artificial continuous rain treatment at low temperatures. The embryo of OS38-5 was highly sensitive to abscisic acid (ABA) at 15degC. Genetic analysis for high dormancy of the seeds was conducted for progeny lines derived from crosses involving OS71 as the donor parent for seed dormancy. The effects of selection on seed dormancy in Fsub(1) plants were found. Genetic segregation of seed dormancy was investigated using Fsub(2) progeny derived from a cross between Kitakeiharu747/OS71 and 16S30/OS71. High dormancy of the seeds seemed to be controlled by several recessive genes. Heritability of seed dormancy in the case of Kitakei-haru747/OS71 and 16S30/OS71 was 0.66 and 0.19, respectively. Wheat of the OS-lines has the following characteristics: low yield, small grain, low lodging and scab resistance, and poor bread-making quality. Therefore, successive crosses between favorable progeny appear to be a promising approach.